Material processing

Abstract

The present invention uses supercritical and near supercritical fluid technology for the processing of polymer-containing formulations without induced foaming, giving benefits of either reduced melt viscosity and/or lower melt temperatures. Its application is particlarly beneficial to difficult to process materials, including unplasticised PVC, polycarbonate, PTFE, UHMWPE and polymers containing high loadings of fillers of organic origin. Shear and thermally sensitive materials can also be processed using this method with less risk of degradation, due to the lower shear input and reduced processing temperatures necessary. The production of foamed ceramic materials and metallic components by such a method is also disclosed.

1 . A method of processing material in a process which requires flow of material including the steps of providing material to process, adding to the material a supercritical or near supercritical fluid to reduce the viscosity of the material and processing the material at its reduced viscosity.  
     
     
         2 . A method according to  claim 1 , wherein the step of processing at lower material viscosity is carried out without causing or allowing the material to foam.  
     
     
         3 . A method according to  claim 2 , wherein the step of processing at a lower viscosity includes maintaining the material above a predetermined pressure.  
     
     
         4 . A method according to any preceding claim, including the step of adding to the material an amount of supercritical fluid which is insufficient to cause foaming to the material.  
     
     
         5 . A method according to any preceding claim, including the step of preventing foaming of the material during processing by control of pressure and/or temperature.  
     
     
         6 . A method according to any preceding claim, including the step of removing the fluid from the material during or after processing thereof.  
     
     
         7 . A method according to  claim 6 , wherein the fluid is removed by positive extraction.  
     
     
         8 . A method according to  claim 7 , wherein positive extraction is carried out by suction  
     
     
         9 . A method according to  claim 7  or  8 , wherein positive extraction is carried out by providing a porous section of processing assembly which retains the material and allows egress of the supercritical fluid.  
     
     
         10 . A method according to  claim 9 , foaming is prevented during processing by control of pressure of the material and fluid combination.  
     
     
         11 . A method according to any preceding claim, wherein the supercritical fluid carbon dioxide.  
     
     
         12 . A method according to any one of  claims 1  to  10 , wherein the supercritical fluid is water.  
     
     
         13 . A method according to any one of  claims 1  to  10 , wherein the supercritical fluid is nitrogen.  
     
     
         14 . A method according to any preceding claim, wherein the process is extrusion or injection moulding.  
     
     
         15 . A system for processing material in a process which requires flow of material including means for containing material to process, means for adding to the material a supercritical or near supercritical fluid to reduce the viscosity of the material and a processing unit operable to process the material at its reduced viscosity.  
     
     
         16 . A system according to  claim 15 , wherein the means for adding a supercritical or near supercritical fluid includes a container of a supercritical or near supercritical fluid.  
     
     
         17 . A system according to  claim 15  or  16 , including control means operable to control the amount of supercritical material added to the material.  
     
     
         18 . A system according to  claim 17 , wherein the control means is operable to add an amount of supercritical or near supercritical fluid insufficient to cause foaming.  
     
     
         19 . A system according to any one of  claims 15  to  18 , including means for removing supercritical or near supercritical fluid from the material during or after processing thereof.  
     
     
         20 . A system according to  claim 19 , wherein the removing means includes a suction device.  
     
     
         21 . A system according to  claim 19  or  20 , wherein the removing means includes a porous section which retains material and allows egress of the supercritical fluid.  
     
     
         22 . A method of processing material in a process which requires flow of material including the steps of providing a material with a viscosity above that required by the process, adding to the material a supercritical fluid in sufficient quantity to reduce the viscosity of the material sufficiently for the process and processing the material at its reduced viscosity.  
     
     
         23 . A method of producing moulded or extruded foamed ceramic articles or components including the steps of providing ceramic material to process, adding to the material a supercritical or near supercritical fluid to reduce the viscosity of the material and processing the material at its reduced viscosity.  
     
     
         24 . A method of producing moulded or extruded foamed metallic articles or components including the steps of providing metal material to process, adding to the material a supercritical or near supercritical fluid to reduce the viscosity of the material and processing the material at its reduced viscosity.